Method of treating bacterial infections

ABSTRACT

A variety of substances are known which induce or alter host resistance to coccic and bacillic infections. It is also known that treatment is complicated by the ability of such organisms to develop resistance to antimicrobials. Numerous strains are known which elaborate enzymes in response to these drugs and thus remain insensitive to them. Hence there appears to be a never-ending demand for anti-coccic and anti-bacillic factors. Certain substituted benzoic acids are shown herein to render the host immune to such strains.

BACKGROUND OF THE INVENTION

This invention pertains to antimicrobials effective in protecting against cocci and bacilli bacterial infections.

Although many antimicrobials have been suggested for the treatment of coccic and bacillic infections, such diseases continue to be a problem. The reason for this is that bacteria such as cocci and bacilli are a unique group of organisms embodying within themselves an array of yet unanswered puzzles in biology, both fundamental and experimental. They are ubiquitous in distribution and have attained extreme degrees of diversification in biological and biochemical characteristics. It is recognized that the significance of staphylococcal infections is not so much in severity, except in a few instances, as in the subtleties of the infection due to the unpredictable vagaries of these organisms.

Treatment of diseases caused by cocci and bacilli is complicated by the ability of the organisms to develop resistance. The magnitude of the problem is further amplified by the extreme difficulty of total eradication, and the frequent reappearance of the same strain even after apparently successful elimination. The inability to eliminate the carrier state by any of the currently known methods and the prevalence of the new antibiotic resistant hospital strains have added a new dimension to the frustrating situation. The development of such multiple antibiotic resistant strains of the organism suggests the desirability of investigating additional means of combatting the infections. As a consequence the development of antimicrobials which are effective against coccic and bacillic infections has attracted considerable attention.

SUMMARY OF THE INVENTION

In accordance with the practice of this invention a new antimicrobial is provided conferring on mammals remarkable resistance to coccus and bacillus infections. The approach is to administer to a mammal suffering from said bacterial infection an antibacterial effective amount of certain para amino and para guanidino benzoic acids. The invention thus provides as an antimicrobial effective in inducing resistance to bacterial infections, yet without the necessity of infection by the organism.

DETAILED DESCRIPTION OF THE INVENTION

The processes of infection leading to coccic infections are accepted to be problems in the ecology of the parasite. It is being increasingly realized that the bacterial and host determinants are closely interrelated. Staphylococcal virulence derives from the combined action of several bacterial factors whose effectiveness is conditioned by the reactions of the host. Perhaps the most striking feature of host-parasite relationships in staphylococcal infections is the relatively atypical immunologic response. Human studies have given convincing evidence that most adult humans possess an array of anti-staphylococcal antibodies. Nevertheless resistance to staphylococci seems to be governed to a considerable extent by other unrelated factors. For example, in the true sense the compounds employed herein are not antibiotics. In vitro tests show that these compounds do not kill the organism. However quite surprisingly, in the system of the host they create an environment in which the organism does not grow. For this reason the compounds are called probiotics. The term probiotics has been proposed to designate compounds which build resistance to infection in the host, but do not inhibit the growth of microorganisms in vitro. Thus they unexpectedly render immunity to the host, as does a vaccine, but without the organism itself being present as it is in vaccines.

The compositions of this invention thus constitute a significant new class of antimicrobials. Specifically they are para substituted benzoic acids wherein the para substitutent is --NH₂, --NHC(NH)NH₂, --CH₂ NH₂, --CH₂ NHC(NH)NH₂, --(CH₂)₂ NH₂, or --(CH₂)₂ NHC(NH)NH₂. It is contemplated that they will be taken orally, or by intramuscular injection.

The probiotics with which this invention is concerned, thus, are p-aminobenzoic acid, p-guanidino benzoic acid, p-aminomethyl benzoic acid, p-guanidinomethyl benzoic acid, p-(β-aminoethyl) benzoic acid and p-(β-guanidinoethyl) benzoic acid. The p-amino benzoic acid was obtained commercially. The aminomethyl and aminoethyl derivatives were prepared from p-bromomethyl or p-bromoethyl benzoic acid by treatment with concentrated ammonium hydroxide. The crude product was purified by means of ion-exchange chromatography and crystallization. The guanidino derivatives were prepared by treating the respective benzoic acid, and either S-methylisothiourea or ammonium thiocyanate with concentrated ammonium hudroxide, the crude product being purified as described.

The high degree of resistance to staphylococcal infections obtained by these para substituted benzoic acids will best be apparent from their biological effects in in vivo tests. In these in vivo tests antistaphylococcic activity was determined using BDF mice, both male and female. The animals were between 9 and 13 weeks old, males having approximate average weights of 12 to 19 grams, females 18 to 24 grams. For the most part the mice were raised and maintained on the Rockland diet.

The assays were conducted using a penicillin-resistant strain, Staphylococcus aureus Original, first isolated from a case of acute tonsilitis and maintained in our laboratories for years. This strain is preserved in the lyophilized form and stored at 0° C. and stock cultures were raised on SA 110 slants once in every 6 months. For testing, the inoculum was prepared as 24 hours cultures from Bacto-Staphylococcus Medium 110. The cells were washed and suspended in physiological saline (TC Tyrode Solution, Difco). In contrast to conventional procedures, a dose killing 80 to 90 percent (LD₈₀₋₉₀) instead of a dose killing 50 percent (LD₅₀) was used in these investigations. This has been the practice in our laboratories in studies with staphylococci since lower dosages often fail to give adequate degrees of mortality. The LD₈₀₋₉₀ was determined by injecting groups of mice subcutaneously with different dilutions of the bacterial suspension and noting the mortality over a 5-day period.

Using groups of six to ten mice, the animals were inoculated subcutaneously two hours before and four hours after challenge with a 60 percent suspension of the "Original Strain" organism. To provide a high dose of para guanidinoethyl benzoic acid which is not completely water soluble, a fine suspension is prepared in cottonseed oil (20 mg/ml:dose, 0.25 ml). Antistaphylococcal activity in vivo is expressed as ASA and as effectiveness of protection using the X² -test and ASA=[(M_(c) -M_(e))/M_(c) ]/C, where M_(c) is the mortality of the untreated negative control, M_(e) is the mortality of the experimental, and C is the dose in millimols. Results of the tests are given in the following table.

    ______________________________________                                         Antistaphylococcal Activity                                                                      Protection                                                                      per Millimol (ASA)                                          Antimicrobial       5 mg dose 1 mg dose                                        ______________________________________                                         Control             none      none                                             p-amino benzoic acid                                                                               29.5      6.17                                             p-guanidino benzoic acid      0.00                                             p-aminomethyl benzoic acid                                                                         65.5      19.53                                            p-guanidinomethyl benzoic acid                                                                               32.11                                            p-(β-aminoethyl) benzoic acid                                                                 65.00     25.11                                            p-(β-aminoguanidinoethyl) benzoic                                          acid                         28.78                                            ______________________________________                                    

The guanidino compounds presented a problem because of their low water solubilities. However our work with them give reason to believe that by other means of administration larger doses will be effective in the case of p-guanidino benzoic acid. All of the other compounds were significantly effective when compared with the untreated negative control using 5 mg doses. Even at 1 mg doses para aminomethyl benzoic acid and para aminoethyl benzoic acid were more effective than the untreated negative control.

The compositions of this invention thus constitute a significant new class of antistaphylococcal agents. It is contemplated that they will be taken orally, say in 250 to 500 milligram tablets. Where exposure to staphylococci or streptococci infections is likely, such as on entering a hospital, injections of say 150 to 500 mg, will be prescribed. The para amino benzoic acid derivatives can be combined with an aqueous medium, vegetable oil, monoglyceride or diglyceride vehicle for injections, sodium chloride being used if necessary to render the solution isotonic. The suspension or solution will contain 0.1 to 5 percent, preferably 0.1 to 1.5 percent of the antimicrobial by weight.

In the case of tablets, if desired, suitable colorants, adhesives, and lubricants will be incorporated along with a solid pharmaceutical diluent, for instance, starches, lactose, sucrose, and other pharmaceutical diluents. These tablets will contain 50 percent to 75 percent of the para amino benzoic acid compound on a weight basis. Capsules can also be made. Thus a process is provided for the control of infections in humans and other mammals due to cocci which involves administering to the mammal an effective amount of the para amino benzoic acid compound. Various diluents, doses, and other variations and modifications will occur to those skilled in the art. Thus it has been pointed out that tablets must be administered more frequently than injections. Such ramifications are deemed to be within the scope of this invention. 

What is claimed is:
 1. A method of treating bacterial infections in mammals comprising administering to a mammal suffering from said bacterial infection an antibacterial effective amount of a para substituted benzoic acid wherein the para substituent is selected from the group consisting of --NHC(NH)NH₂, --CH₂ NH₂, --CH₂ NHC(NH)NH₂, --(CH₂)₂ NH₂, and --(CH₂)₂ NHC(NH)NH₂.
 2. The method of claim 1 wherein the para substituted benzoic acid is p-aminomethyl benzoic.
 3. The method of claim 1 wherein the para substituted benzoic acid is p-guanidinomethyl benzoic acid.
 4. The method of claim 1 wherein the para substituted benzoic acid is p-(β-aminoethyl) benzoic acid.
 5. The method of claim 1 wherein the para substituted benzoic acid is p-(β-guanidinoethyl) benzoic acid. 